Troubleshooting Tip : How to troubleshoot application virtual wan link (VWL) crash

The System Event log may show that the application VWL crashed.

Example of the crash :

diagnose debug crashlog read

16343: 2025-09-02 14:05:53 <27739> firmware FortiGate-200E v7.4.8,build2795b2795,250523 (GA.M) (Release)
16344: 2025-09-02 14:05:53 <27739> application vwl
16345: 2025-09-02 14:05:53 <27739> *** signal 6 (Aborted) received ***
16346: 2025-09-02 14:05:53 <27739> Register dump:
16347: 2025-09-02 14:05:53 <27739> RAX: 0000000000000000 RBX: 00007f55d5e45300
16348: 2025-09-02 14:05:53 <27739> RCX: ffffffffffffffff RDX: 0000000000000000
16349: 2025-09-02 14:05:53 <27739> R08: 0000000000000000 R09: 00007fffa4739870
16350: 2025-09-02 14:05:53 <27739> R10: 0000000000000008 R11: 0000000000000246
16351: 2025-09-02 14:05:53 <27739> R12: 00007fffa4739ae0 R13: 0000000000001000
16352: 2025-09-02 14:05:53 <27739> R14: 0000000000000010 R15: 00007f55d390c000
16353: 2025-09-02 14:05:53 <27739> RSI: 00007fffa4739870 RDI: 0000000000000002
16354: 2025-09-02 14:05:53 <27739> RBP: 00007fffa4739bc0 RSP: 00007fffa4739870
16355: 2025-09-02 14:05:53 <27739> RIP: 00007f55d8a3ce41 EFLAGS: 0000000000000246
16356: 2025-09-02 14:05:53 <27739> CS: 0033 FS: 0000 GS: 0000
16357: 2025-09-02 14:05:53 <27739> Trap: 0000000000000000 Error: 0000000000000000
16358: 2025-09-02 14:05:53 <27739> OldMask: 0000000000000000
16359: 2025-09-02 14:05:53 <27739> CR2: 0000000000000000
16360: 2025-09-02 14:05:53 <27739> stack: 0x7fffa4739870 - 0x7fffa473ab80
16361: 2025-09-02 14:05:53 <27739> Backtrace:
16362: 2025-09-02 14:05:53 <27739> [0x7f55d8a3ce41] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16363: 2025-09-02 14:05:53 <27739> [0x7f55d8a26557] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16364: 2025-09-02 14:05:53 <27739> [0x7f55d8a7e370] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16365: 2025-09-02 14:05:53 <27739> [0x7f55d8a8572a] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16366: 2025-09-02 14:05:53 <27739> [0x7f55d8a88a14] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16367: 2025-09-02 14:05:53 <27739> [0x7f55d8a8abb1] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16368: 2025-09-02 14:05:53 <27739> [0x7f55daef8551] => /bin/vwl {0x7f55d939e000} => vwl_service_optimize_member_reorder at ././daemon/vwl/vwl_service.c:2397
16369: 2025-09-02 14:05:53 <27739> [0x7f55daef8b5f] => /bin/vwl {0x7f55d939e000} => vwl_service_member_reorder_need at ././daemon/vwl/vwl_service.c:2643
16370: 2025-09-02 14:05:53 <27739> [0x7f55daef9733] => /bin/vwl {0x7f55d939e000} => vwl_service_do_install at ././daemon/vwl/vwl_service.c:2840
16371: 2025-09-02 14:05:53 <27739> [0x7f55daef9b73] => /bin/vwl {0x7f55d939e000} => vwl_service_install at ././daemon/vwl/vwl_service.c:2866
16372: 2025-09-02 14:05:53 <27739> [0x7f55dadf3612] => /bin/vwl {0x7f55d939e000} => check_expiration at ././migbase/sysapi/timer/timer.c:206
16373: 2025-09-02 14:05:53 <27739> [0x7f55dadf1c18] => /bin/vwl {0x7f55d939e000} => _fg_avl_traverse at ././migbase/sysapi/timer/fg_avl_tree.c:46
16374: 2025-09-02 14:05:53 <27739> [0x7f55daeec346] => /bin/vwl {0x7f55d939e000} => vwl_main at ././daemon/vwl/vwl_main.c:84
16375: 2025-09-02 14:05:53 <27739> [0x7f55d96fa952] => /bin/vwl {0x7f55d939e000} => fortiexecve at ././sysinit/fortiexec.c:878
16376: 2025-09-02 14:05:53 <27739> [0x7f55d97005fb] => /bin/vwl {0x7f55d939e000} => run_initentry at ././sysinit/init.c:1000
16377: 2025-09-02 14:05:53 <27739> [0x7f55d9700da6] => /bin/vwl {0x7f55d939e000} => run_initlevel at ././sysinit/init.c:1187
16378: 2025-09-02 14:05:53 <27739> [0x7f55d97037ae] => /bin/vwl {0x7f55d939e000} => initd_mainloop at ././sysinit/init.c:2554
16379: 2025-09-02 14:05:53 <27739> [0x7f55d970433b] => /bin/vwl {0x7f55d939e000} => main at ././sysinit/init.c:3038
16380: 2025-09-02 14:05:53 <27739> [0x7f55d8a27e1b] => /lib/libc.so.6 {0x7f55d8a04000} => ?? ??:0
16381: 2025-09-02 14:05:53 <27739> [0x7f55d96f5d2a] => /bin/vwl {0x7f55d939e000} => _start at /build/glibc/glibc-2.30/csu/../sysdeps/x86_64/start.S:122
16382: 2025-09-02 14:05:53 <27739> fortidev 6.0.2.0008
16383: 2025-09-02 14:05:53 the killed daemon is /bin/vwl: status=0x6

VWL is the Virtual WAN Link daemon related to SD-WAN features.

There may be several reasons causing the crash.

Things to take notes :

1. How often does the crash happen: it could be a one-time event, and can be ignored if no service impact. If it frequently happens, then further investigation may be done.
2. Any recent change to the SD-WAN setting. Compare the timestamp of the config change and the crashed time.
3. Any recent firmware upgrade/downgrade. The crash could happen on some versions only.
4. Open a Technical Support ticket to investigate further.